The normal way of forming profiles grooves in the sides of a key blank made of a durable material, such as brass, or so called “nickel silver”, or some other metal alloy, is to use a rotating cutter disc which operates in a side surface of the key blank so that the material is cut away and a groove is formed, while moving the axis of the cutter disc linearly along the key blank.
However, the shape of the profile groove formed by such a conventional method is limited. Of course, the disc can be oriented at an angle relative to the key blank surface, and it is also possible to modify the shape of the peripheral, active surface of the cutter disc to some extent. Even so, there are numerous geometrical shapes of profile grooves that need other or additional forming methods, in particular undercut profile grooves of various geometrical shapes.
It is known per se to use linearly guided punching tools with one or more teeth, such as broaches with several teeth, for making profile grooves in key blanks. See e.g. the published international patent application WO/2010/095997 (WINLOC AG), page 2, last paragraph. Such tools are guided and forced linearly in parallel to the key blank while forming a profile groove, such as an undercut groove.
However, there are limitations as to the possible geometrical shapes that can be made with such punching tools. The forces are very strong, and there is a clear risk that the material of the key blade will start to float adjacent to the groove being formed in this way, especially if the wall between the inside of the groove and the outer surface of the key blank is relatively thin. Thus, there is a great risk that the key blade will be deformed during this forming process, making the finished key useless.